The present invention relates to a method of forming a boron-doped diamond film by chemical vapor deposition, and in particular to a method of forming a boron-doped diamond film by chemical vapor deposition (CVD) utilizing a two-component system reactant gas doped with trimethyl-borate.
Recently, utilizing semiconductive diamond films to fabricate semiconductor electronics has attracted the attentions of many researchers. Due to their wider energy gap (5.45 eV at room temperature), which causes a higher breakdown field in the fabricated electronic components, together with their surface stability at high temperature (500.degree.-600.degree. C. in air, 1400.degree.-1700.degree. C. in inert gas), diamond films have been used in the fabrication of many electronic components operated in a high temperature ambient.
Although Schottky diodes and blue light emitting diodes have been fabricated recently from diamond films, the polycrystalline nature and high defect density of these diamond films prepared by CVD pose a severe limitation on their use in semiconductor electronic components.
In order to synthesize semiconducting diamond films of better quality, many fundamental studies of low pressure plasma CVD growth process have been done. Many reports have indicated that boron-doped diamond films can be successfully formed on a silicon substrate by the CVD process during low pressure synthesis if a boron-containing reactant gas system is used, and the deposited films are found to exhibit semiconducting properties similar to that of single crystal natural diamond. However, these low pressure syntheses have a disadvantage of using toxic diborane as a dopant source.
R. Meilunas et al have reported that the morphology of the deposited diamond films can be improved, if a C.sub.2 H.sub.2 --O.sub.2 --H.sub.2 three-component system reactant gas which is doped with trimethyl borate is used as a raw material during the CVD process of depositing diamond films on the substrate (The Physical and Electrical Properties of Boron Doped Diamond Thin Films, Proc, 2nd Int'l cont, on Elec. Mats, 81990Material Research Society, 609-614). Although nontoxic trimethyl borate is used as a dopant source that is safer in operation, the doped boron is not uniformly distributed over the entire depth of the resultant diamond film. As a result, the diamond film fabricated by this method is not satisfactory.